Copy milling device

ABSTRACT

Apparatus for tracing the contour of a shaped member including a platform adapted to mount a shaped member and a feeler mounted on a carrying head and adapted to engage the shaped member, means tending to maintain the feeler in engagement with the shaped member, and servomotor devices coupled to the platform for movement of the platform respectively in directions at right angles to each other to trace the contour of said shaped member, the velocity of said devices being controlled by velocity control means, for example, valves or other movement-sensing means actuated by the aforesaid movement of said feeler and the feeler being rigidly mounted on a first arm which, in turn, is pivotally mounted intermediate its ends on a second arm for movement about an axis parallel to the longitudinal axis of the feeler, the second arm being pivotally mounted on the carrying head for movement about a second axis parallel to and spaced from the first axis, the end of the first arm remote from the feeler actuating the velocity control means.

United States Patent [72] Inventor Patrick William Agnew Kilsyth Glasgow, Scotland [21] App]. No. 809,083

[22] Filed Mar. 21, 1969 [45] Patented Nov. 2, 1971 [73] Assignee Precision Hydraulics Limited Glasgow, Scotland [32] Priority Mar. 21, 1968 [3 3] Great Britain [54] COPY MILLING DEVICE 2,911,182 11/1959 Clarke etal.

3,174,403 3/1965 McCoy 3,399,600 9/1968 Agnew Primary Examiner-M. Cary Nelson Assistant ExaminerRichard Gerard Attorney-Mason, Fenwick & Lawrence ABSTRACT: Apparatus for tracing the contour of a shaped member including a platform adapted to mount a shaped member and a feeler mounted on a carrying head and adapted to engage the shaped member, means tending to maintain the feeler in engagement with the shaped member, and servomotor devices coupled to the platform for movement of the platform respectively in directions at right angles to each other to trace the contour of said shaped member, the velocity of said devices being controlled by velocity control means, for example, valves or other movement-sensing means actuated by the aforesaid movement of said feeler and the feeler being rigidly mounted on a first arm which, in turn, is pivotally mounted intermediate its ends on a second arm for movement about an axis parallel to the longitudinal axis of the feeler, the second arm being pivotally mounted on the carrying head for movement about a second axis parallel to and spaced from the first axis, the end of the first arm remote from the feeler actuating the velocity control means.

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SHEET 30F 3 lnuenlor pAT WILLIAM Acmew Ynwm naunzucu ltorneys COPY MILLING DEVICE This invention relates to apparatus for use in following or tracing the contour of a shaped member.

Normally apparatus for tracing the contour of a shaped member includes a platform adapted to mount a shaped member and a feeler mounted on a carrying head and adapted to engage the shaped member, means tending to maintain the feeler in engagement with the shaped member, and servomotor devices coupled to the platform for movement of the platform respectively in directions at right angles to each other to trace the contour of said shaped-member, the velocity of said devices being controlled by velocity control means, for example, valves or other movement-sensing means actuated by the aforesaid movement of said feeler, such apparatus being referred to hereinafter as apparatus of the type aforesaid.

According to the present invention there is provided apparatus of the type aforesaid including a feeler, a first and a second arm, the feeler being rigidly mounted on said first arm which, in turn is pivotally mounted intennediate its ends on the second arm for movement about an axis parallel to the longitudinal axis of the feeler, the second arm being pivotally mounted on the carrying head for movement about a second axis parallel to and spaced from the first axis, the end of the first arm remote from the feeler actuating the velocity control.

Embodiments of the present invention will now be described, by way of example, with reference to the accompanying drawings, in which:

FIG. 1 shows a feeler-mounting arrangement FIG. 2 shows an automatically controlled tracing apparatus and FIG. 3 shows a manually controlled tracing apparatus.

The drawings show a vertical feeler 1 rigidly mounted on two spaced horizontal parallel first arms 2 and 3, the arms in turn being mounted for pivotal movement about an axis BB FIG. 1 on a second arm 4 by means of ball bearings 9 which are adjustable to take up backlash. This second arm 4 takes the form of a stirrup and its end remote from the first arm is pivotally mounted about an axis AA (FIG. 1) on the carrying head of the apparatus again by adjustable ball bearings (not shown). The end of the upper horizontal arm 3 is provided with an extension 5 having a cylindrical bore 6 which embraces the part-spherical outer surface 7 ofthe valve member 8 of a disc valve FIGS. 2 and 3. The axes AA and 88 about which the first and second arms pivot are mutually parallel to the longitudinal axis of the feeler l and thus the feeler is constrained to point always in a vertical direction, however, any movement of the feeler 1 in a horizontal direction causes a corresponding movement of the valve member 8. The maximum displacement of the feeler tip is in the order of 0.01 inch and since the effective length of the arms is in the order of 1 inch the displacement of the valve member 8 from its center position is equal to that of the feeler; the displacements along the axis of the first arms 2, 3 being in the same sense as those of the feeler and the displacements at right angles to the axis of arms 2 and 3 being in the opposite sense.

The valve member 8 is disc shaped and has two concentric raised rims 10,11 on either side, the inner raised rims l1 defining two cylindrical recesses 12 and 13 while between the inner and outer raised rims annular recesses 14 and 15 are defined. The cylindrical recesses 12 and 13 on opposite sides of the member are joined by a bore 16 of frustoconical shape. The valve member 8 is accommodated in a valve chamber formed in the carrying head 17 and has a sliding fit within this chamber. Two first valve ports 18, (only one of which is shown in H68. 2 and 3) are formed in the bottom face of the chamber and are spaced 90 apart and positioned at such a radius that when the valve member 8 is in its center undisplaced position the inner rim 11 protruding from the bottom of the valve member completely covers the ports 18. Each of these ports 18 is in fluid communication with a hydraulic piston and cylinder device (not shown) the purpose of which will be described below. A further port 19 is provided in the bottom face of the valve chamber, this port providing for fluid communication between the annular recess 15 and a fluid reservoir.

The carrying head 17 below the valve member 8 is provided with a central bore 20 in which is accommodated a valve-centralizing rod 21, this rod being provided at its upper end with a conical surface 22 corresponding to the frustoconical bore 16 in the member. The rod 21 is capable of axial movement into and out of the valve chamber 8 and feed rate adjusting means, part of which are shown at 23, are provided to hold the rod in its adjusted position. With the rod 21 in its fully raised position the conical surfaces 16,22 of the member and rod abut and movement of the member 8 is prevented, while on lowering the rod, a limited amount of movement of the member is permitted. The rod 21 is provided with a through bore 24 and this bore is in fluid communication with the high-pressure side of the pump which takes its fluid from the aforesaid reservoir..

Thus, pressure fluid is supplied to the cylindrical recesses l2, 13 in the valve chamber and, dependent on the displacement of the valve member, to the piston and cylinder devices. Similarly, again dependent on the displacement of the valve member, exhaust of fluid from the piston and cylinder devices through the first ports 18 to the annular recess 15 and thence to the reservoir by way of ports 19 is possible.

In the embodiment illustrated in FIG. 2 a similar arrangement of second ports 18 is provided in the upper face of the chamber, two second ports being provided spaced l apart and closable by the inner raised rim 11 on the top of the valve member 8 when the valve member is in its central position.

The piston and cylinder devices are arranged at right angles to each other and move a table on which a shaped member is rigidly mounted. The feeler abuts the periphery of this shaped member and thus movement of the table causes displacement of the feeler l and corresponding movement of the valve member 8, this controlling the supply and exhaust of fluid to and from the devices and causing the devices to move the table in such a manner that the profile of the shaped member or template is traced. This mode of operation is described in US. Pat. No. 3,399,600.

Spring means are provided to maintain the feeler 1 in contact with the shaped member and these means include a sleeve 30 rotatably mounted on the carrying head 17 and a bellcrank 31 pivotally mounted at the lower end of the sleeve 30. The bellcrank 31 carries a roller 32 at the end of one of its arms 33, which roller 32 abuts the feeler 1 and the end of its other arm 34 is attached to a tension spring 35 which is mounted within the sleeve 30. An adjustable spring anchorage 36 is provided at the other end of the sleeve and thus the bellcrank roller 32 is, at all times, urged into contact with the feeler 1. It is desirable to maintain the force exerted on the feeler l at all times at the same angle to the profile of the template and in this respect means are provided to rotate the sleeve 30 and thus the bellcrank 31.

Said means include a radial piston motor accommodated in the carrying head 17, this motor comprising a shaft 40 rotatably mounted with its axis concentric with the axis of the valve member 8 in its undisplaced position. The cam or eccentric of the motor takes the form of a cam surface 41 which is at all times parallel to the axis of the shaft 40 but varies progressively in radius. At least three pistons in the form of balls 42 (only one of which is shown) act on this surface 41 and the balls are accommodated in cylinders 43, the axes of which are perpendicular to the shaft axis, the periphery of each ball 42 abuts the cammed surface and movements of the balls are obtained by supplying pressure fluid from the valve chamber by way of the second ports 18 to that part of the cylinder on the side of the balls 42 remote from the shaft 40, an increase of pressure fluid to this side of the balls causing inward movement of the balls which, in turn, causes rotation of the shaft. Exhaust of fluid from the cylinder 43 is by way of a bore 44 leading to the annular recess 14 in the valve chamber. The upper end of the shaft 40 carries a gear wheel 45 of similar diameter a further gear wheel 46 fixed to the top of the sleeve 30. Thus, displacement of the feeler 1 is relayed to the valve member 8 which partially uncovers at least one of the second ports 18, this allowing the introduction of pressure fluid to the swashplate motor, such that its shaft rotates the shaft 40 in proportion to the amount of fluid supplied, and this rotation is transmitted by way of gears 45, 46 to the sleeve 30 such that the angle of the spring force on the template remains the same. The reverse gear train has a ratio of 1:1 since the arms 2,3,4, connecting the feeler 1 to the valve member 8 cause the member to describe a small circle anticlockwise if the feeler describes a similar small clockwise circle. Consequently, the direction of spring loading on the feeler must rotate in the opposite direction to the motor. The gear 45 mounted on the motor shaft 40 may be declutched from the shaft to allow for manual manipulation of the tracing head for setting up or other purposes.

In a second embodiment shown in FIG. 3 the radial piston motor is dispensed with and rotation of the sleeve 30 is performed manually.

lclaim:

1. Apparatus of the type aforesaid including a feeler, a first and a second arm means, the feeler being rigidly mounted on said first arm means which, in turn, is pivotally mounted intermediate its ends on the second arm means for movement about an axis parallel to the longitudinal axis of the feeler, the second ann means being pivotally mounted on a carrying head for movement about a second axis parallel to and spaced from the first axis, the end of the first arm means remote from the feeler actuating a velocity control means.

2. Apparatus as claimed in claim 1, in which the first arm means includes two parallel-spaced members each pivoted intermediate its ends on the second arm means and each rigidly fixed to the feeler, one member carrying the velocity control actuating means.

3. Apparatus as claimed in claim 1, in which the pivotal mountings for the arm means comprise adjustable ball bearings.

4. Apparatus as claimed in claim 1, in which the velocity control means comprises valve means including a chamber defined in the carrying head and having parallel-facing faces, and a member slidably mounted between said faces, said member being movable by the feeler and having corresponding concentric cylindrical and annular recesses in its opposite faces and a central through passage, pressure fluid ports in communication with said cylindrical and annular recesses at all positions of the member and ports in the facing faces separately closable by said member and adapted to be placed in fluid communication with piston and cylinder devices.

5. Apparatus as claimed in claim 4, in which the port in communication with the cylindrical recesses is connectable to a first source of fluid pressure and the port in communication with the annular recesses is connectable to a second source of pressure fluid, the pressure of the first source being greater than that of the second source.

6. Apparatus as claimed in claim 4, in which the through passage in the member is frustoconical and a rod movable in a direction into and out of the chamber is provided with a corresponding frustoconical end engageable in the passage such that the position of the rod determines the freedom of movement of the member.

7. Apparatus as claimed in claim 6, in which the rod has a through bore which acts as the port in the chamber in communication with the said first source.

8. Apparatus as claimed in claim 4, in which the member is provided with a part-spherical periphery and the valve-actuating end of the first arm means comprises a ring in which the member is engaged.

9. Apparatus as claimed in claim 4, in which the carrying head includes also a radial piston motor operable by fluid led from additional ports in communication with the chamber of the valve means, the output shaft of said motor engaging by way of a gear train a rotatable part of the carrying head.

10. Apparatus as claimed in 9, in which the said additional ports are located in the facing faces of the chamber and are separately closable by said member, such that the supply and exhaust of fluid to and from the motor is dependent upon the position of the member within the chamber.

11. Apparatus as claimed in claim 9, in which the gear tram is a reversing gear train having a 1:1 ratio.

12. Apparatus as claimed in claim 1 including means tending to maintain the feeler in engagement with a shaped member, which includes a bellcrank having a roller abutting the feeler, the bellcrank being pivotally mounted on the carrying head and spring urged towards the feeler.

13. Apparatus as claimed in claim 12, in which the spring is a tension spring attached between the bellcrank and an adjustable anchorage held on the carrying head.

14. Apparatus as claimed in claim 12, in which that part of the carrying head supporting the bellcrank is rotatable about the axis of the feeler such that the direction of the force exerted on the feeler by the bellcrank is always substantially at the same angle to the shaped member at the point of contact of the feeler and the member. 

1. Apparatus of the type aforesaid including a feeler, a first and a second arm means, the feeler being rigidly mounted on said first arm means which, in turn, is pivotally mounted intermediate its ends on the second arm means for movement about an axis parallel to the longitudinal axis of the feeler, the second arm means being pivotally mounted on a carrying head for movement about a second axis parallel to and spaced from the first axis, the end of the first arm means remote from the feeler actuating a velocity control means.
 2. Apparatus as claimed in claim 1, in which the first arm means includes two parallel-spaced members each pivoted intermediate its ends on the second arm means and each rigidly fixed to the feeler, one member carrying the velocity control actuating means.
 3. APparatus as claimed in claim 1, in which the pivotal mountings for the arm means comprise adjustable ball bearings.
 4. Apparatus as claimed in claim 1, in which the velocity control means comprises valve means including a chamber defined in the carrying head and having parallel-facing faces, and a member slidably mounted between said faces, said member being movable by the feeler and having corresponding concentric cylindrical and annular recesses in its opposite faces and a central through passage, pressure fluid ports in communication with said cylindrical and annular recesses at all positions of the member and ports in the facing faces separately closable by said member and adapted to be placed in fluid communication with piston and cylinder devices.
 5. Apparatus as claimed in claim 4, in which the port in communication with the cylindrical recesses is connectable to a first source of fluid pressure and the port in communication with the annular recesses is connectable to a second source of pressure fluid, the pressure of the first source being greater than that of the second source.
 6. Apparatus as claimed in claim 4, in which the through passage in the member is frustoconical and a rod movable in a direction into and out of the chamber is provided with a corresponding frustoconical end engageable in the passage such that the position of the rod determines the freedom of movement of the member.
 7. Apparatus as claimed in claim 6, in which the rod has a through bore which acts as the port in the chamber in communication with the said first source.
 8. Apparatus as claimed in claim 4, in which the member is provided with a part-spherical periphery and the valve-actuating end of the first arm means comprises a ring in which the member is engaged.
 9. Apparatus as claimed in claim 4, in which the carrying head includes also a radial piston motor operable by fluid led from additional ports in communication with the chamber of the valve means, the output shaft of said motor engaging by way of a gear train a rotatable part of the carrying head.
 10. Apparatus as claimed in 9, in which the said additional ports are located in the facing faces of the chamber and are separately closable by said member, such that the supply and exhaust of fluid to and from the motor is dependent upon the position of the member within the chamber.
 11. Apparatus as claimed in claim 9, in which the gear train is a reversing gear train having a 1:1 ratio.
 12. Apparatus as claimed in claim 1 including means tending to maintain the feeler in engagement with a shaped member, which includes a bellcrank having a roller abutting the feeler, the bellcrank being pivotally mounted on the carrying head and spring urged towards the feeler.
 13. Apparatus as claimed in claim 12, in which the spring is a tension spring attached between the bellcrank and an adjustable anchorage held on the carrying head.
 14. Apparatus as claimed in claim 12, in which that part of the carrying head supporting the bellcrank is rotatable about the axis of the feeler such that the direction of the force exerted on the feeler by the bellcrank is always substantially at the same angle to the shaped member at the point of contact of the feeler and the member. 